In computer systems, local direct current batteries may provide backup power to certain portions of the computer system. A battery can be described as local if it supplies power to only a component or collection of components in the computer system.
As an example, a RAID card of a server system may include a local battery that provides backup power to a local cache of the RAID card. A RAID card is typically coupled to the PCI slot of a server system or may be integrated into the motherboard through the PCI bus of such a system. A RAID card acts as a RAID controller, controlling the operation of the array of drives that comprise the RAID subsystem. The operation of the server system and the RAID subsystem often requires that the RAID card coordinate writes of data to the drives of the RAID subsystem. To facilitate the writing of data to the drives of the RAID subsystem, a RAID card will often include a local cache. When writing data from the RAID card to a drive of the RAID subsystem, it is preferable that the data be sent in burst format, rather than as isolated, individual writes to a drive of the drive array. To transmit data in burst format to a drive of the RAID subsystem, it is useful to collect or cache up the data in the local cache located on the RAID card. Because the local cache of the RAID card may, for a limited period, store data that has not yet been written to a drive of the RAID subsystem, the RAID card will include a local battery that is coupled to the cache of the RAID card. The presence of the local battery provides backup power to the cache in the event of a power loss to the RAID card. In this manner, if there is a loss of power to the RAID card, the presence of the local battery that is coupled to the cache of the RAID card insures that the volatile data stored in the local cache is not lost.
As a second example of the use of local batteries for system components, Dell Computer's Remote Administration Card (DRAC) may also include a local battery. In operation the DRAC card plugs into a PCI slot of a server system. A DRAC card is a diagnostic tool that assists Dell or other qualified support personnel with the provision of technical support to the server system. If the server becomes inoperable for some reason, diagnostic equipment may be coupled to the DRAC card to diagnosis the failure in the server. The local battery in the DRAC card allows the DRAC card and its associated diagnosis function to operate even in the case of a power failure to the server. In this manner, even if the server has lost power, the DRAC card will operate from its local battery to allow the diagnosis of the failure experienced by the server. The DRAC card also allows for administration or operation of a server from a remote site. According to this function, a remote user can control certain functions of the server from a remote site.
One difficulty presented by a local battery is the possible of battery dissipation following manufacture and prior to receipt of the computer system by the customer. The dissipation of a local battery can occur following manufacture and during shipment. Local batteries are often charged during the manufacturing process. The manufacturing process may also result in the battery being coupled to its load. In this manner, once the A/C power source to the server system is removed following the testing of the server system at the manufacturer's site, the local battery will attempt to supply power to the load. Over time, if the local battery remains connected to the load in the absence of an A/C power source to the server system, the local battery will dissipate and may arrive at the customer in an uncharged condition.
When the computer system is shipped to the customer, it is desirable that any local batteries arrive at the customer in a charged condition. If a local batteries do not arrive at the customer in a charged and functional condition, the backup capability that was intended to be provided by the local battery is compromised or missing entirely. In the case of the RAID card, for example, the RAID card will begin to collect data in the local cache immediately upon operation of the server and RAID subsystem. Recharging of the local battery of a RAID card will typically take between four and eight hours. If the local battery of the RAID card is not yet recharged and the RAID card suffers a power loss during its initial several hours of operation, any data in the local cache may be lost. In this example, because the local battery was discharged during shipment, a sudden loss of power occurring prior to the time when the local battery was recharged at the customer's site may result in the loss of data. In the case of a DRAC card, if the local battery of the DRAC card is not charged at the time the system reaches the customer, the DRAC card will not be functional if there is a loss of power to the server system that occurs prior to the time the local battery of the DRAC card is recharged. For these reasons, it is desirable that local batteries of the computer system not be discharged during manufacturing or shipment, but instead arrive at the customer in a charged condition.
To avoid discharge of a backup battery during shipment, one possible solution is to physically disconnect the battery from its load during shipment. Although an uncoupled battery will experience some residual dissipation, the dissipation will be much less than the relatively quick dissipation experienced by a battery that is coupled to its load during shipment. Third party manufacturers of RAID controllers, for example, often physically disconnect the local battery from the RAID controller prior to shipment. The customer or user, upon receipt of the RAID controller, will have to physically reconnect the local battery to the RAID card at the time of installation of the RAID card in the server system.
In the case of integrated computer systems, however, physically disconnecting and physically connecting a local battery to its load is not a preferable solution. First, such a solution requires significant, and undesirable, customer involvement in the installation process. According to such a solution, the user would be required to open the computer system and make the necessary connection as part of the user's installation process. This process would require considerable skill on the part of the user in opening the computer system, locating the affected component, making the necessary connection, and closing the computer system without damaging any elements of the computer system. Second, such a solution would require that the battery be physically disconnected during the manufacturing process. After a Dell computer system is fully assembled, including the connection of the local batteries to their respective loads, the system goes through a quick test and an extended test procedure. Following a successful test, it is desirable that the systems not be physically opened thereafter. Leaving the case of the computer system closed following the quick test and extended test procedures insures that no configuration changes are made to the system and that the system that is actually shipped to the customer is the same system that passed all required testing procedures. Thus, once the local batteries have been coupled to their loads and the test procedures have been successfully completed, opening the system to physically uncouple the local batteries would compromise the configuration and testing integrity of the computer system.